Thaniel

A limited slip will put SOME torque to the wheel with better traction. How much torque is dependant on the preload torque of the diff. However the rest of the torque is going to go out the wheel with the least traction. This means one wheel will spin when the rear wheels have extremely different amounts of traction.

In the 4x4 world a good way to test between a locker and a limited slip is to jack up one drive wheel and put a brick infront of the other. With a limited slip the car can not drive over the brick. I did this on a vehicle where the preload torque on the diff is so high I could not rotate the tire by hand (mad me think it was a locker) but when trying to drive over the brick, once the engine over comes the preload toruqe (which the it did easily) the wheel spun like an open diff.

By the way, I have never gotten a car with an open diff to spin both rear wheels at the same time. Cars that I have driven that had opens diffs and did the one wheely peely.

'87 Nissan maxima
'89 Mercury cougar
'78 Datsun 200sx
'82 Datsun 200sx
S-10 pickup
Chevy Astro van
Various other trucks.

If you can get both rear wheels to spin at the same time you don't have a open diff.

NA86RULZ

can anyone explain this (I believe someone either typed wrong or I am wrong):

When on dry pavement, if i drop the clutch at high enough RPMs, I have to strips. However, when I dump the cluth cornering, only the inside tire leaves a strip. Isn't this contradicting??

Mike
---------
'86 NA
no mods

Icemark

Sounds like an open diff, and poor rear traction.

rxspeed87

ok what would be the point of a viscious or clutch type lsd if they do not transfer power to the wheel with more traction, and they do not lock the tires up like a locker would.

not trying to be a smart *** but better understand different LSD types

pearlwing

86 Base NA, dropped my clutch on dirt, got 2 marks

Icemark

Okay the 5 main types of diffs:

Open: Just that a conventional open diff, no locking. However if both wheels have poor traction (from smaller tires, bad or worn suspension, or whatever) and the vehicle is moving straight, it is not un-common to have both wheels spin.

Locked: Both wheels spin exactly the same no matter what the traction is on either wheel hard to drive in high traction situations like the street). This is used more often in drag cars, 4WD trucks or offroad vehicles (and in fact is found on my TRD Tacoma as a electronic switchable engagment, stock from the factory)

Clutch type (sometimes called Posi-traction by less informed types, but Posi is just a brand name): a mechanical clutch plate(s) engage when one wheel spins faster than another, in severe traction loss it can "lock up" the axles simular to a Locked diff. Often wears out fast in bad climates where traction is lost easily (like high snow or rain climates).

Fluid type: a silicon fluid is suspended between perfed plates. When one wheel looses traction and spins faster than the other wheel, the fluid heats up and locks to together the plates and two wheels. Lockup can be changed by composition of the fluid. Because of the slow engagement it is generally not used in race or off road vehicles. But other than the open type it is the next lightest, and reasonably cheap to manufacture.

Torsen type: works as an open diff until one wheel looses traction and then the diff transfers the power to the wheel with the most traction (simular to the auto 4WD systems on porsche and Ford vehicles). Also the most expensive to manufacture.

There are several other subtypes and variations, but that gives you the basics.

rxspeed87

so my comment about transfering power to the wheel with the most traction is in a round about way correct I would say


granted doesn´t do it in the same for as a torsen does it
but if your pass side wheel is on good ground and your driver side is on slick stuff and it starts to spin the clutch/fluid type lsd will then try to send power to the non slipping wheel by attempting to lock them together when a difference in spin speed is present

now for my next question

have always heard good abou tthe torsen rear and though I have also heard it is not the best for drag racing it is very good for road racing.... can you get one for a FC and if so where and how much_

Icemark

yes a Torsen ususally doesn't like the shear that drags tend to subject it too. And you want both wheels getting the most power, not the wheel that has the best traction.

as far as getting a Torsen, what application??? NA???

If yes, then you can use a 94+ Miata Torsen diff. You would use the NA pinoin and gear, but the Miata guts.

If a T2 in therory the FD Torsen LSD should work, but I haven't personally done it, so I am not sure how far you have to disassemble and modify.

Icemark

And No, I wouldn't agree. A fluid or clutch type simply locks the axle, only a Torsen shifts the power.

In fact thats the draw back to the Torsen, that it shifts power to the wheel with the most traction (generally up to 80% of the power). So it is possible that the majority of the power is going only to one wheel.

With the lock, clutch type, or fluid type, they generally send equal power to both wheels, regardless of traction once they have locked.

rxspeed87

ok another question

why would you want to hae equal power going to both wheels?
I can understand if you are going straight b/c there should be equal traction
but in a turn if you give both wheels equal traction then you could be wasting power by giving your inside wheel enough power to spin it while if you shift some of that power to the outside wheel with more grip you should have less of a chance of losing traction and be able to put more power to the ground?

Icemark

I was refering to drag 1/4 mile stuff and that a Torsen is not the best choice for those applications.

Cost aside, a Torsen is far superior in street or road racing applications, than a clutch type or any other type LSD. That is why you found them on the FD or the upper/sportier models of the Miata.

rxspeed87

thanks for the help

where can I get some info for swapping the miata torsen into my FC

and if I was to have a TII diff how would I get a torsen in them?


also the FD uses a torsen right?

rxspeed87

well I am stumped once again


I ended up putting my tires on different traction again

right tire on dirt
left of pavement


spun the tires


the right tire started spinning at first then was followed by a chirp of my left tire and a good surge of accel a second later